Cancer cells are cells that basically bypass any sort of regulatory processes in the cell cycle (and mitosis - the splitting of the cell). This leads to uncontrollable cell growth/duplication which hence leads to more and more cancerous cells. Cancer itself is so hard to cure for a couple of different reasons. If the cells are in the form of a benign tumor, that is a tumor that does not spread from its original infected tissue, it should be "easy" to remove with surgery. However, if it metastasizes, or spreads into surrounding tissues through the lymph or blood systems, then it becomes even harder to remove because of its far reach and complex structure. Also, cancer cells can be simply described as normal body cells that have gone rogue. That being said, things such as antibiotics, that are designed to get rid of foreign bodies, cannot get rid of cancerous cells without getting rid of most of your regular body cells as well simply because they cannot tell the difference.
Hope this helps :)
C the earth because that is the only planet around so he thought that the sun and everything else rotated around us.
Answer: Gas giants are larger, have more moons, and are less dense. They also are outer planets. Terrestrial planets are more dense, have a rocky and hard surface, and less moons sometimes no moons. They are called the inner planets.
